A. Field of the Invention
The invention relates to a process for synthesizing ammonia complexes of zinc alkylene bisdithiocarbamates starting from carbon disulfide, ammonia, an alkylenediamine and zinc oxide.
B. Description of the Prior Art
Such products are known as fungicides, especially zinc ethylene bisdithiocarbamate, also known as "Zineb". According to West German Pat. No. 1,226,361 ammonia complexes of zinc ethylene bisdithiocarbamate it can be synthesized in the following ways:
(a) from the Zineb.2NH.sub.3 complex by acidification;
(b) from an aqueous Zineb suspension by prolonged stirring with an aqueous ammonia solution; and
(c) from a water-soluble salt of ethylene bisdithiocarbamic acid by reaction with a water-soluble zinc salt in the presence of 1 mole of ammonia per mole of zinc salt.
In addition, Austrian Pat. No. 195,440 teaches the following methods of synthesis:
(d) reacting an aqueous solution of ammonium ethylene bisdithiocarbamate with zinc oxide; and
(e) allowing zinc oxide to react with the necessary quantities of the starting materials needed for the formation of ammonium dithiocarbamate.
Austrian Pat. No. 195,440 discusses only zinc ethylene bisdithiocarbamate, but does not disclose the ammonia complexes thereof. From the examples, is it not obvious whether any, or which, ammonia complexes are formed. Accordingly, it is unclear what must be done to obtain selectively the ammonia complex with one NH.sub.3 molecule per zinc atom.